The effect of an asymmetric core on convection in Enceladus' ice shell: Implications for south polar tectonics and heat flux

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Abstract

Enceladus exhibits a strong tectonic contrast between its south polar terrain (SPT), which is young and geologically active, and its northern hemisphere, which is relatively ancient and stable. Previous global three-dimensional (3-D) spherical models of convection exhibit patterns that are symmetrical around the equator and fail to explain the formation of a hemispheric dichotomy. Here we present global 3-D spherical models of convection in Enceladus' ice shell to show that convection in Enceladus' ice shell with plasticity and irregular core geometry can self-consistently generate a hemispheric dichotomy in tectonics and heat flux. With a spherical core, convection produces global overturning, which cannot explain the regional confinement of Enceladus' current tectonic activity to the SPT. Models with appropriate nonspherical core geometry and plasticity tend to produce overturning confined to the SPT or regional overturning in different regions at different times, which can explain the tectonic dichotomy and local age differences on Enceladus. Our models predict heat flows up to 5-10 gigawattts (GW) during active episodes, consistent with Cassini observations. Key Points Previous models have failed to explain Enceladus' hemispheric dichotomy We show that such a dichotomy emerges naturally from irregular core topography Episodic activity explains high current heat flux yet low time-mean power

Original languageEnglish (US)
Pages (from-to)5610-5614
Number of pages5
JournalGeophysical Research Letters
Volume40
Issue number21
DOIs
StatePublished - Nov 16 2013

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Enceladus
dichotomies
heat flux
tectonics
ice
convection
shell
plastic properties
plasticity
geometry
Northern Hemisphere
equators
heat transmission
heat flow
high current
effect
topography

Keywords

  • cryovolcanism
  • icy satellites
  • mantle convection
  • Spacecraft missions (Cassini)
  • tectonics

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Geophysics

Cite this

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title = "The effect of an asymmetric core on convection in Enceladus' ice shell: Implications for south polar tectonics and heat flux",
abstract = "Enceladus exhibits a strong tectonic contrast between its south polar terrain (SPT), which is young and geologically active, and its northern hemisphere, which is relatively ancient and stable. Previous global three-dimensional (3-D) spherical models of convection exhibit patterns that are symmetrical around the equator and fail to explain the formation of a hemispheric dichotomy. Here we present global 3-D spherical models of convection in Enceladus' ice shell to show that convection in Enceladus' ice shell with plasticity and irregular core geometry can self-consistently generate a hemispheric dichotomy in tectonics and heat flux. With a spherical core, convection produces global overturning, which cannot explain the regional confinement of Enceladus' current tectonic activity to the SPT. Models with appropriate nonspherical core geometry and plasticity tend to produce overturning confined to the SPT or regional overturning in different regions at different times, which can explain the tectonic dichotomy and local age differences on Enceladus. Our models predict heat flows up to 5-10 gigawattts (GW) during active episodes, consistent with Cassini observations. Key Points Previous models have failed to explain Enceladus' hemispheric dichotomy We show that such a dichotomy emerges naturally from irregular core topography Episodic activity explains high current heat flux yet low time-mean power",
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T1 - The effect of an asymmetric core on convection in Enceladus' ice shell

T2 - Implications for south polar tectonics and heat flux

AU - Showman, Adam

AU - Han, Lijie

AU - Hubbard, William B.

PY - 2013/11/16

Y1 - 2013/11/16

N2 - Enceladus exhibits a strong tectonic contrast between its south polar terrain (SPT), which is young and geologically active, and its northern hemisphere, which is relatively ancient and stable. Previous global three-dimensional (3-D) spherical models of convection exhibit patterns that are symmetrical around the equator and fail to explain the formation of a hemispheric dichotomy. Here we present global 3-D spherical models of convection in Enceladus' ice shell to show that convection in Enceladus' ice shell with plasticity and irregular core geometry can self-consistently generate a hemispheric dichotomy in tectonics and heat flux. With a spherical core, convection produces global overturning, which cannot explain the regional confinement of Enceladus' current tectonic activity to the SPT. Models with appropriate nonspherical core geometry and plasticity tend to produce overturning confined to the SPT or regional overturning in different regions at different times, which can explain the tectonic dichotomy and local age differences on Enceladus. Our models predict heat flows up to 5-10 gigawattts (GW) during active episodes, consistent with Cassini observations. Key Points Previous models have failed to explain Enceladus' hemispheric dichotomy We show that such a dichotomy emerges naturally from irregular core topography Episodic activity explains high current heat flux yet low time-mean power

AB - Enceladus exhibits a strong tectonic contrast between its south polar terrain (SPT), which is young and geologically active, and its northern hemisphere, which is relatively ancient and stable. Previous global three-dimensional (3-D) spherical models of convection exhibit patterns that are symmetrical around the equator and fail to explain the formation of a hemispheric dichotomy. Here we present global 3-D spherical models of convection in Enceladus' ice shell to show that convection in Enceladus' ice shell with plasticity and irregular core geometry can self-consistently generate a hemispheric dichotomy in tectonics and heat flux. With a spherical core, convection produces global overturning, which cannot explain the regional confinement of Enceladus' current tectonic activity to the SPT. Models with appropriate nonspherical core geometry and plasticity tend to produce overturning confined to the SPT or regional overturning in different regions at different times, which can explain the tectonic dichotomy and local age differences on Enceladus. Our models predict heat flows up to 5-10 gigawattts (GW) during active episodes, consistent with Cassini observations. Key Points Previous models have failed to explain Enceladus' hemispheric dichotomy We show that such a dichotomy emerges naturally from irregular core topography Episodic activity explains high current heat flux yet low time-mean power

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KW - mantle convection

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